you can essentially build a circuit with anything that has two distinct states. On/Off is one of the simplest. Direction of current will be a LOT more complicated to implement though I would imagine it could be done.

In terms of FET (field effect transistor) logic, you need a gate (transistor), or maybe two FETs at each end of the wire. That's expensive use of resources. FET logic is on/off logic in use in today's consumer gadgets.

50 years ago Current Mode Logic (CML), using bipolar transistors, would steer current (in the same direction) down one of two parallel wires. Also expensive, but very fast for the time. But it ran hot/consumed lots of expensive power. And it took up twice the surface area when running wires.

SQUID logic devices (superconductive) can use magnetic loops for bit storage and superconductive tunneling junctions for gates/switches. Maybe you could put TJs at each end of a magnetic loop and store the bits as north/south alternatives distinguished by the direction of the current in the loop. This cryogenic technology operates at roughly liquid nitrogen and colder temperatures. The great thing about cryogenic superconductive logic is that it can perform power-dissipation-free computation for free. As long as the computation is performed in a closed system, no power is dissipated. Power dissipation comes only when the computing system has to send information to and from the outside, ambient temperature world. Like your room.

I do not know what you want to do, but if you are using alternating currents frequency as a medium for binary information processing I think you would require really high frequencies to make anything worth mentioning with it (unless you are more about making sensors). Look:

"A 32nm transistor can switch on and off over 300 billion times in one second. It would take you 4000 years to flick a light switch on and off that many times."
-Intel Corporation

Click to expand...

After seeing that I think that a source of alternate current of a frequency of equal to or greater than 300GHz looks pretty hard to find. Unless you use transistors to achieve such an alternation, but what would be the point then if in the end you are using transistors. (you know, 60 bits per second doesn't look like much information processing power to me)

What I mean is that there are better ways of processing binary information unless you can actually make a brain like structure in which information is processed differently (but that won't be binary and if it is it would be a very inneficient brain structure when working at low frequencies).